1. Field
Embodiments of the present invention relate to an actuator system, a lithographic apparatus, a method of controlling the position of a component and a method for manufacturing a device.
2. Background
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
The requirements for any component to be used within a lithographic apparatus are very strict. In particular, it is often necessary for the component to operate in a precise manner, namely with high accuracy. It is also typically necessary for the component to be able to operate without having any impact on other components within the apparatus. For example, in a lithographic apparatus that transfers a pattern to a substrate using EUV radiation, many components may be required to operate within a vacuum chamber. Therefore, such components must be compatible with low pressure environments. In particular, it may be important to ensure that no outgassing occurs at low pressures. For components that require control systems, this may be particularly difficult because of the constraints imposed on, for example, wires providing control signals from a controller, that may be outside of the vacuum chamber, to the component, that may be inside the vacuum chamber.
Furthermore, due to their complexity, lithographic apparatus may be relatively expensive. Accordingly, it is continually necessary to ensure that each component is not unduly expensive in order to ensure that the overall cost of the lithographic apparatus does not become excessive. For components such as actuators, additional requirements for their use within a lithographic apparatus may include speed of response.
Piezoelectric actuators have previously been used as actuators with lithographic apparatus. However, known piezoelectric actuators may be relatively expensive. In addition, known piezoelectric actuator systems typically require a relatively complex control system and many connecting wires to control them, both further increasing the costs, in particular in relation to their use in a vacuum chamber.